| 1. |
- El Aamrani, Abdelaziz, et al.
(författare)
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Synthesis, crystal Structure and temperature induced phase transition in Ba1/5Sr4/5NiMoO6 double perovskite oxide: : Study by X-ray diffraction and Raman spectroscopy
- 2017
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Ingår i: Journal of Applied Surfaces and Interfaces. ; 2:1-3, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- BaCO3, SrCO3, NiO, MoO3 precursors were used as starting materials in the synthesis of double perovskite Ba1/5Sr4/5NiMoO6, and their crystal structure at room tempertaure was solved using X-ray powder diffraction. The Rietveld analysis of X–ray powder diffraction patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a= 5.58537(1) Å, c=7.9066(2) Å. The structure can be represented as a three-dimensional network of alternating NiO6 and MoO6 octahedra, with Ba and Sr atoms occupying the interstitial spaces. Temperature-induced phase transitions of Ba1/5Sr4/5NiMoO6 were investigated by mean of Raman spectroscopy technique at high temperature up to 392 °C. remarkable in the behaviuor of temperature dependence of the modes has been interpreted as a phase transition from the tetragonal (I4/m) to the cubic () structure.
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| 2. |
- El Hachmi, Abdelhadi, et al.
(författare)
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Temperature induced structural phase transition in Sr3-xCaxFe2TeO9 (0 <= x <= 1) probed by Raman and Mossbauer techniques
- 2017
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1141, s. 484-494
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Tidskriftsartikel (refereegranskat)abstract
- A series of perovskites Sr3-xCaxFe2TeO9 (0 <= x <= 1) have been prepared in polycrystalline form by solid-state reaction method in air. These materials have been studied by X-ray powder diffraction method (XRPD) and Raman spectroscopy. An analysis of the XRD patterns at room temperature has shown that these compounds crystallize in a tetragonal system, space group I4/m. The structure contains alternating (Fe/Te)(2a)O-6 and (Fe/Te)(2b)O-6 octahedra, tilted in anti-phase in the basal ab-plane. The study of Raman spectroscopy at various temperatures shows a transition from tetragonal to cubic phase: I4/m -> Fm (3) over bar m. This phase transition occurs at high-temperature. Analysis of Raman spectra recorded at several temperatures shows that this phase transition appears near similar to 375 degrees C for (x = 0), similar to 435 degrees C for (x = 0.5) and similar to 451 degrees C for (x = 1). A proportional and gradual increase of temperature phase transition is observed as function of the calcium amount.
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| 3. |
- El Hachmi, Abdelhadi, et al.
(författare)
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Synthesis and Rietveld refinements of new ceramics Sr2CaFe2WO9 and Sr2PbFe2TeO9 perovskites
- 2018
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Ingår i: Powder Diffraction. - : J C P D S-INT CENTRE DIFFRACTION DATA. - 0885-7156 .- 1945-7413. ; 33:2, s. 134-140
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Tidskriftsartikel (refereegranskat)abstract
- Ceramics of Sr2CaFe2WO9 and Sr2PbFe2TeO9 double perovskites have been prepared in polycrystalline form by solid-state technique, in the air. The crystalline structure was analyzed using X-ray powder diffraction (XRPD) at room temperature. Rietveld analysis of XRPD) patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a = 5.5453(1) angstrom, c = 7.8389(1) angstrom for Sr(2)CaFc(2)WO(9), and a = 5.5994(15) angstrom, c = 7.8979(30) angstrom for Sr2PbFe2TeO9. A certain degree of anti-site disordering of W and/or Te and Fe on the B -sites have been detected, indicating the presence of a partial amount of W and/or Te at Fe positions and vice versa.
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